Needle guides



P 5, 1957 E. s. CLARKE ETAL 3,339,510

NEEDLE GUIDES Filed June 21, 1965 /0- I Inventors:

Kaye/7e 5, C/arke Herber/ LZ/n/efl Ray P f/a/cb Jr. Sfephe/v P LofarS/r/Patented Sept. 5, 1967 3,339,510 NEEDLE GUIDES Eugene S. Clarke,Georgetown, Herbert L. Elwell, Rockport, Roy P. Hatch, Jr., Essex, andStephen P. Lotarski, Beverly, Mass., assignors to United Shoe MachineryCorporation, Flemington, N.J., a corporation of New Jersey Filed June21, 1965, Ser. No. 465,524 4 Claims. (Cl. 112-227) ABSTRACT OF THEDISCLOSURE A needle guide for a curved needle sewing machine in whichthe needle is guided in a curved guideway formed in a hard insert bondedto a ferrous body of the guide.

The present invention relates generally to improvements in needle guidesfor curved needle sewing machines and more particularly to such needleguides in which superior wear characteristics are obtained by a needlereceiving passageway formed in an insert of extremely hard wearresistant material such as a cemented carbide.

In shoe inseam sewing machines such as that disclosed in Patent No.3,088,426, issued May 7, 1963, upon application of Lloyd G. Miller andin outsole sewing machines such as that disclosed in application forUnited States Letters Patent Serial No. 422,853 filed Dec. 31, 1964 inthe names of Joseph R. Ioannilli, Mieth Maeser and Kenneth H. Rauschke,curved needles are employed for penetrating resistive shoe parts to formstitches. In such machines the needle is supported against deflection bya needle guide which includes a curved passage formed to provide asliding fit for the needle. Because of elastic deformation of the needlein penetrating the work piece and the heat of friction generated inmodern high sewing speeds, such conventional needle guides wear rapidlyand must be discarded after a short period of use because the passage isenlarged by wear and affords insufiicient reinforcement or' stiffeningto the needle. It has been estimated that in inseam sewing machinesaccording to the above Miller patent operated at high speed, theconventional needle guide must be replaced after 20 to 25 hours ofoperation. Such frequent replacement is both costly and time consuming.

It is accordingly an object of the present invention to improve thedurability of needle guide for curved needles and of similar articlessubjected to severe wear.

Another object of the invention is to provide a method and apparatus forforming arcuate passages accurately in extremely hard materials.

According to a feature of the invention the needle guiding passage orguideway is formed in an insert of cemented carbide. Although an insertof hardened high speed steel or of various compositions of cementedcarbide may be fixed in position in the guide by silver soldering forexample, it has been found that adequate accuracy of location and bondstrength of the insert to the body of the guide as well as greatereconomy of manufacture is obtained by casting the insert as a part of aninvestment steel casting for example during the molding process. Inorder to resist the high pouring temperature of the steel it has beenfound that the heat resistance of chromium carbide bonded with nickel issufficient so that the mechanical properties of the insert are notimpaired. The insert is imperforate and the curved passage is formed byelectrical discharge machining or EDM.

The foregoing objects and features and numerous advantages of theinvention will be more fully appreciated from the following detaileddescription of an illustrative embodiment taken in connection with theaccompanying drawings in which:

FIG. 1 is a fragmentary view in right side elevation of a shoe inseamsewing machine including a curved needle supported by a needle guideaccording to the present invention;

FIG. 2 is a fragmentary view in side elevation and partially in sectionshowing the apparatus for forming a curved passage in a needle guide;

FIG. 3 is a view in front elevation of the apparatus depicted in FIG. 2;

FIG. 4 is a fragmentary view in front elevation partly in section and onan enlarged scale showing the curved passage in the process of beingformed in a needle guide; and

FIG. 5 is a fragmentary view on an enlarged scale of a portion of aneedle guide shown being completed in a subsequent operation.

Turning now to the drawings, there is illustrated in FIG. 1 a view ofinstrumentalities surrounding the sewing point of a shoe inseam sewingmachine such as that disclosed in the above identified Millerapplication. The machine is employed for inserting a seam 10 which joinstogether an upstanding rib 12 on an insole 14, the margin of an upper 16and a welt 18 while the shoe parts are supported on a last 19. Themachine includes a curved hook needle 20, which is supported againstdeflection by a needle guide 22. In addition, the machine also includesnormal instrumentalities of inseam sewing machines as well as an awl 24,a channel guide 26, a thread finger 28, a looper 30, and a Welt guide32. The various parts of the machine already enumerated are operated ina conventional manner and serve merely to improve the understanding ofthe invention which relates to the needle guide 22. During normal sewingoperations the needle 20 is oscillated at high speeds with respect tothe needle guide 22 including a pair of spaced apart wear resistantinserts 34 in which a curved passage 36 is formed to provide a slidingfit for the needle 20.

The needle guide 22 shown in FIG. 1 is one in which two inserts 34 areemployed with a slot 37 between the two inserts to provide an additionaledge for scraping olf wax and other material which adhere to the needlefrom its contact with the thread. In the other views there is shown analternative needle guide construction including a body 38 in which issecured a single wear resistant insert 40 having a length approximatelyequal to the distance between the exterior end faces of the inserts 34.In either case whether the single or double insert construction isinvolved the first step in the manufacturing of the needle guide is theproduction of a needle guide blank preferably by precision casting. Inthe casting step, an insert of sintered chromium carbide bonded withnickel such as Carboloy grade No. 608 manufactured by the GeneralElectric Co., is positioned in the mold in much the same manner as acore would be placed to form an aperture in the casting. The metalsolidifies and secures the insert in position for conventional machiningoperations, which include the finishing to size of a mounting hole 42 tobe fitted upon a needle stud 44 about whose axis the needle 20 isoscillated as seen in FIG. 1. After the conventional machiningoperations have been completed electrical discharge machining or EDM isemployed for forming a curved passage 46 concentric with a mounting hole47 in the needle guide employing a single insert 40 or alternativelyconcentric with the hole 42 in the needle guide employing the spacedapart inserts 34. The use of such machines for forming straight holes inextremely hard work pieces is already known. Methods of forming curvedholes in relatively soft materials using slim shanked rotary cuttingsuch curved hole machining the maximum attainable hole depth thereforeis a function of hole diameter, radius of curvature and shank diametereven though the length may be doubled by machining from both ends. Inthepractice of the present invention not only can much harder materials bemachined but also the length of the curved hole is unlimited forpractical purposes. It is accordingly possible to obtain far superiordurability because of harder materials as well as greater length ofbearing in curved guideways.

The formation of the curved passage 46 is illustrated in FIGS. 2-4inclusive in conjunction with a fragmentarily illustrated commercial EDMapparatus such as that manufactured by the Elox Corporation of Troy,Michigan. Various features of the machine are disclosed in United StatesLetters Patent including Nos. 2,415,690 in the name of A. A. Hilfelderand 2,996,638 and 3,062,192 in the name of R. S. Webb. In general, theEDM process is carried out by successive high intensity electricaldischarge across a gap 48 as seen in FIG. 4. The Webb patents pertain todevices for accurately positioning an electrode carrying piston tomaintain optimum spacial relationship between the electrode and the workpiece by advancing the electrode along a straight line path in EDMapparatus.

In the present drawings the piston of the machine is designated byreference character 50 and in accordance with the usual practice has astraight line operating motion downwardly toward and upwardly away froma tank 52. Contained in the tank 52 is a quantity of coolant-electrolyte54in which the work piece is submerged. The conventional EDM apparatusincludes a servo-system responsive to are striking potential or toaverage current for maintaining the piston 50 constantly positioned soas to provide an optimum gap between an electrode fixedly supported onthe piston 50 and the work piece submerged in the coolant-electrolyte54.

In FIG. 2 conventional electrical sensing apparatus for positioning theelectrode and a power supply to provide the necessary current for theEDM operation are designated merely as a block 56 having a positiveelectrical connection to a collar 58 and a negative connection groundedat 60. It will be seen from FIG. 3 that the piston 50 is also groundedat 62.

The collar 58 is part of a fixture which together with the needle guideblank 38 is mounted in the tank 52 and submerged in the body ofcoolant-electrolyte 54. The fixture which is electrically grounded at 64includes an electrically conductive base 66 on which is mounted a stud68 having an outer threaded end bearing a clamping knob 70. The stud 68and the knob 70 are metallic and in contact with the base 66 andconsequently also at ground potential. There is interposed between thecollar 58 and stud 68 electrical insulation comprising a headed bushing72 and a washer 74 to isolate the collar and the blank 38 electricallyfrom the grounded parts already described and also from an electrode 76which is also maintained at ground potential so that the full potentialof the power supply 56 is developed across the gap 48. The electrode 76is a curved tube including an interior passage 78 through whichelectrolyte-coolant is pumped continuously from a flexible tube 80connected to the end of the electrode most remote from the blank 38.Between the electrode 76 and the piston 50 there are connections totranslate the straight -line motion of the piston into a pivotal motionof the end-of the electrode about the axis of the stud 68. Theseconnections include a rod 82 retained in a collet at the lower end ofthe piston 50. The electrode 76 is maintained on a sector 84 by a clampplate 86 and the rod 82 is connected to the sector by a link 88 pivotedto the rod and link at 90 and 92 respectively. As a result of theconnections already described, whenever the piston 50 in response to ahigh are striking voltage descends toward the tank 52, the descendingmotion of the piston is translated into a counterclockwise motion of theelectrode 76 thereby narrowing the gap 48. A rise of the piston 50 issimilarly translated into a clockwise motion of the electrode 76 andconsequent widening of the gap 48.

The blank 38 is retained against turning about the axis of the stud 68by a pair of fingers 94 and 96 placed ahead and behind the insert 40respectively. The electrode 76 may be employed for initially machiningits own arcuate guideway 98 in the finger 94 merely by insulating thebase 66 from ground and connecting it to the positive terminal of thepower supply 56 thus applying the electrical discharge machiningpotential across a gap between the electrode and the finger 94. In orderto insulate the car 94, which with the electrode 76 during subsequentmachining operations is at ground potential, a slotted insulator 100 isretained by an undercut recess in the finger 94 and its outer surface102 receives the end surface of the insert 48. A clearance passage 104for the electrode 76 is formed in the insulator 100. Similarly thefinger 96 is provided with an insulator 106 and formed with a clearancepassage 108. The insulator 106 which also has a clearance passage 110contacts the insert 40 and thus maintains the insert insulated from thebase 66.

It is thus seen that the electrode 76 is directed by the accuratelyformed guideway 98 and that as the right end of the electrode as seen inFIGURE 4 approaches the left end of the insert 40 in an imperforateinsert, the sensing apparatus of the machine continues to advance theelectrode toward the insert 40 until the proper gap 48 is established.Successive electrical discharges of the machine cause erosion of theinsert in the path of the electrode As the erosion of the workpiececontinues the electrode 76 is also eroded and the required pivotalmotion of the carrier 84 to maintain optimum width of the gap 48 iscontinuously provided by vertical self adjustment of the piston 50. Boththe work piece and the electrode are cooled and flushed bycoolant-electrolyte introduced through the passage 78, and theelectrolyte in the gap 48 also regulates in a predictable manner thecurrent flow across the gap.

After the guideway 46 has been completely formed by electrical dischargemachining, a further operation is desirable to complete the needle guideparticularly when the guideway is formed in .an extremenly hard materialsuch as a cemented carbine. This operation depicted in FIG. 5 consistsof forming a small radius 112 at each end of the guideway 46 so as toreduce the possibility of the carbine to dig in and thus gouge thesofter material of the needle 20 thereby reducing the useful life of theneedle. The radius 112 may conveniently be formed by manually holdingthe end of the guideway 46 against a formed rotating diamond wheel 114.

In the appended claims, the article is defined in terms of hardmaterials. Numerous materials are useful in carrying out the presentinvention and the term hard should be interpreted as characteristic notonly of materials which resist penetration under load but also ofmaterials which have the wear characteristic and heat resistance atleast equivalent to those hardened tool steels. Such materials arecharacterized by difficulty of machining by conventional apparatuscomprising sharp edge cutting tools. In some cases particularly inalloys of cobalt, and chromium such as some Stellites, the hardness maybe as low as 50 Rockwell C but such materials defy practical machiningby means of edged cutting tools. The term hard material is thereforeintended to include a broad range of ferrous and nonferrous materialswhich are diflicult to machine but provide improved wearcharacteristics.

Having thus disclosed out invention what is claimed as new and desiredto secure by Letters Patent of the United States is:

1. A needle guide for reinforcing a curved needle comprising a ferousbody, a hard insert bonded to the ferrous body and having a pair ofexposed outer end faces and a curved guideway extending between the endfaces and contained entirely within the insert.

2. A needle guide according to claim 1 in which the insert consists ofcemented chromium carbide.

5 6 3. A needle according to claim 2 in which the insert radius at theintersection of the guideway with each end is bonded directly to theferrous body. face.

4. A needle guide for reinforcing a curved needle com- No referencescited prising a ferrous body, a hardened insert bonded to the ferrousbody and having a pair of exposed outer end faces 5 JORDAN FRANKLINPrimwy Examiner and a curved guideway extending between the end faces,

contained entirely Within the insert and formed with a RICHARD J.SCANLAN, JR., Examiner.

1. A NEEDLE GUIDE FOR REINFORCING A CURVED NEEDLE COMPRISING A FEROUSBODY, A HARD INSERT BONDED TO THE FERROUS BODY AND HAVING A PAIR OFEXPOSED OUTER END FACES AND A CURVED GUIDEWAY EXTENDING BETWEEN THE ENDFACES AND CONTAINED ENTIRELY WITHIN THE INSERT.